The effectiveness of short-video narrative ads is highly contingent on the alignment between exposure duration and content features. When virtual endorsers are introduced, the proportion of their on-screen presence may emerge as a pivotal new variable, generating complex synergistic effects with narrative storytelling and time constraints. This study investigates how, under varying exposure durations and ad types, the proportion of virtual endorser presence influences consumer behavioral response through cognitive load and emotional response.
A multi-method approach was employed across two studies. Study 1 utilized secondary data analysis of 579 ads from Douyin to examine the interaction effect between exposure duration and ad type. Study 2 adopted a 3 (exposure duration: short/medium/long) × 2 (ad type: narrative/non-narrative) × 3 (virtual endorser proportion: none/low/high) between-subjects experimental design with 810 participants. PROCESS macro for SPSS with bootstrap methods was applied to test the chain-mediating roles of cognitive load and emotional response, and the moderating effect of virtual endorser proportion.
Results indicate that: (1) behavioral response for narrative ads peaks under medium duration (30–100 seconds), and this advantage is amplified by a high proportion of virtual endorser presence; (2) cognitive load and emotional response play a conditional chain-mediating role; (3) under short duration, a high proportion of virtual endorser presence exacerbates cognitive overload, leading to lower evaluations; under long duration, its effect is weakened due to attentional disengagement; the optimal cognitive investment-to-emotional conversion efficiency is achieved with narrative ads featuring a high proportion of virtual endorsers under medium duration.
Theoretically, this research extends virtual endorser studies from static imagery to the dynamic dimension of on-screen proportion, proposing the optimal salience and load balance hypothesis. Practically, it provides marketers with a triadic optimization strategy.
